This application claims priority to International Application No. PCT/GB99/03268 which was published on Apr. 20, 2000.
The invention relates to a vacuum cleaner. Particularly, but not exclusively, the invention relates to an upright vacuum cleaner.
An upright vacuum cleaner generally has a cleaner head rotatably mounted on the lower end of a main body in which dust separation apparatus is housed. The dust separation apparatus can be in the form of a conventional bag filter or in the form of a cyclonic separator consisting of one or two cyclones as shown and described in, for example, EP 0 042 723. A handle for propelling the cleaner across the floor to be cleaned is arranged to extend upwardly from or behind the main body. A pair of supporting wheels are mounted on the lower end of the main body or on the cleaner head. The cleaner head extends in a forward direction. A dirty-air inlet is located at the forward end of the cleaner head and facing downwardly so that, in use, the dirty-air inlet faces towards the surface to be cleaned. Dirty air is drawn into the dust separation apparatus via the dirty-air inlet by means of a fan driven by a motor. It is conducted to the dust separation apparatus by a first air flow path. When the dirt and dust entrained within the air has been separated from the airflow in the separating apparatus, clean air is conducted to the clean air outlet via a second air flow path and expelled into the atmosphere.
Upright vacuum cleaners are commonly convertible into cylinder cleaners. In the cylinder mode, the dirty air is drawn into the cleaner by way of a wand or hose attached to the vacuum cleaner instead of by way of the dirty air inlet located in the cleaner head. This cylinder mode facilitates cleaning of areas which cannot be easily reached by the cleaner head, for example, underneath furniture, on stairs or above the floor. The handle which is used to propel the vacuum cleaner across the floor in the upright mode is in some cases convertible into a wand and hose arrangement for this purpose. In either mode, the air which is drawn into the machine has to travel along an air flow path of significant length before being expelled to the atmosphere.
In the known prior art, the air flow path changes in cross-sectional size and shape whilst conducting the air from the dirty air inlet to the dirt and dust separating apparatus and then to the clean air outlet of the vacuum cleaner. The air flow path also normally follows a route which forces the air flow path to change direction abruptly or else to expand in cross-sectional area. This is because the shape and cross-sectional area of different portions of the air flow paths are often determined by the relative proportions of different parts of the vacuum cleaner. For example, the portion of the air flow path immediately downstream of the changeover valve which selects the dirty air inlet appropriate to upright cleaning or cylinder cleaning is often significantly larger in cross-section than other portions of the air flow path so that incoming air from either inlet can be accepted into the downstream flow path. These variations in cross-section of the air flow path cause frictional losses resulting in pressure drops within the air flow, which results in reduced performance of the vacuum cleaner. Air flow paths in prior art vacuum cleaners have also included sharp bends and corners, which also contribute to frictional losses and pressure drops.
It is an object of the present invention to provide a vacuum cleaner in which frictional losses and pressure drops are minimised. It is a further object of the invention to provide a vacuum cleaner having an airflow path which is less prone to blocking and accumulation of dirt and dust than known vacuum cleaners. A still further object is to provide a vacuum cleaner in which the parts of the airflow path which are prone to blocking are more easily accessible than in known vacuum cleaners.
The uniform cross-sectional area of the air flow path ensures that frictional losses and pressure drops are kept to a minimum and that the dust separation apparatus may thus function at maximum efficiency. The preferred circular cross-sectional area of substantially 800 mm2 has been found to be particularly effective when the vacuum cleaner includes dust separation apparatus consisting of a cyclonic separator.
The provision of removable portions housing curved parts of the air flow path allows the user of the apparatus to remove the removable portions should any blockages occur in the said curved portions. The removal of a removable portion gives the user of the apparatus easy access to the air flow path which allows removal of blockages quickly and easily. The removable portions are preferably retained in an operational position with respect to the remainder of the apparatus by quick release fastenings, for example, resilient tabs, to enable an unskilled user of the apparatus to carry out basic maintenance and removal of blockages. This reduces the amount of skilled time required to maintain the apparatus and keeps the apparatus operational for longer periods thus increasing user satisfaction and decreasing the amount of time required for maintenance and repair.